Railroad diagram
Circa: It covers the initial circa date value.
Date: It defines a format for how a date can be specified.
Pre keyword: It specifies the optional circa definition.
Period: It indicates a time period.
Post keyword: It is word or phrase indicating time direction.
Earliest date: It is the initial date value (from).
Latest date: It is the subsequent date value (to).
Recent period: These are the keywords to identify recent time periods.
Eon: These are the keywords to identify recent geological periods.
Time period: These are the keywords to identify historical epochs.
Era: These are the keywords to identify distinctive historical time periods.
Month: This includes the months of the year.
Number: This includes numerical digits.
Year digit: This includes digits of the year.
Day digit: This includes days of the month.
Date value: This includes definition of a date.
Age: This includes periods of human history.
Paleolithic: This includes the anthropological period.
Dynasty: This includes the sequences of rulers of the same family.
Kingdom: This includes the realms or provinces of nature.
Japan period: This includes distinctive Japanese time periods.
Middle east: This includes the distinctive middle eastern time periods.
